linux-kernel - Re: [PATCH bpf-next v3 2/2] selftests/bpf: use canonical ftrace path

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Date:   Fri, 10 Mar 2023 18:33:52 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     zwisler@...nel.org
Cc:     bpf@...r.kernel.org, linux-kernel@...r.kernel.org,
        Ross Zwisler <zwisler@...gle.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Andrii Nakryiko <andrii@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Hao Luo <haoluo@...gle.com>, Jason Gunthorpe <jgg@...pe.ca>,
        Jiri Olsa <jolsa@...nel.org>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        Leon Romanovsky <leon@...nel.org>,
        Martin KaFai Lau <martin.lau@...ux.dev>,
        Mykola Lysenko <mykolal@...com>, Shuah Khan <shuah@...nel.org>,
        Song Liu <song@...nel.org>,
        Stanislav Fomichev <sdf@...gle.com>,
        Yonghong Song <yhs@...com>, linux-kselftest@...r.kernel.org,
        linux-rdma@...r.kernel.org, linux-trace-kernel@...r.kernel.org,
        "Michael S . Tsirkin" <mst@...hat.com>
Subject: Re: [PATCH bpf-next v3 2/2] selftests/bpf: use canonical ftrace
 path

On Fri, 10 Mar 2023 10:52:09 -0700
zwisler@...nel.org wrote:

> diff --git a/tools/testing/selftests/bpf/get_cgroup_id_user.c b/tools/testing/selftests/bpf/get_cgroup_id_user.c
> index 156743cf5870..4fa61ac8a0ee 100644
> --- a/tools/testing/selftests/bpf/get_cgroup_id_user.c
> +++ b/tools/testing/selftests/bpf/get_cgroup_id_user.c
> @@ -86,8 +86,12 @@ int main(int argc, char **argv)
>  	pid = getpid();
>  	bpf_map_update_elem(pidmap_fd, &key, &pid, 0);
>  
> -	snprintf(buf, sizeof(buf),
> -		 "/sys/kernel/debug/tracing/events/%s/id", probe_name);
> +	if (access("/sys/kernel/tracing/trace", F_OK) == 0)
> +		snprintf(buf, sizeof(buf),
> +			 "/sys/kernel/tracing/events/%s/id", probe_name);
> +	else
> +		snprintf(buf, sizeof(buf),
> +			 "/sys/kernel/debug/tracing/events/%s/id", probe_name);

I don't know how the BPF folks feel, but I do know some kernel developers
prefer that if you need to break a single command into multiple lines that
you then need to add brackets around it. As it makes it easier to read.

	if (access("/sys/kernel/tracing/trace", F_OK) == 0) {
		snprintf(buf, sizeof(buf),
			 "/sys/kernel/tracing/events/%s/id", probe_name);
	} else {
		snprintf(buf, sizeof(buf),
			 "/sys/kernel/debug/tracing/events/%s/id", probe_name);
	}



>  	efd = open(buf, O_RDONLY, 0);
>  	if (CHECK(efd < 0, "open", "err %d errno %d\n", efd, errno))
>  		goto close_prog;
> diff --git a/tools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c b/tools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c
> index 113dba349a57..22be0a9a5a0a 100644
> --- a/tools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c
> +++ b/tools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c
> @@ -338,7 +338,12 @@ static int get_syms(char ***symsp, size_t *cntp, bool kernel)
>  	 * Filtering out duplicates by using hashmap__add, which won't
>  	 * add existing entry.
>  	 */
> -	f = fopen("/sys/kernel/debug/tracing/available_filter_functions", "r");
> +
> +	if (access("/sys/kernel/tracing/trace", F_OK) == 0)
> +		f = fopen("/sys/kernel/tracing/available_filter_functions", "r");
> +	else
> +		f = fopen("/sys/kernel/debug/tracing/available_filter_functions", "r");
> +
>  	if (!f)
>  		return -EINVAL;
>  
> diff --git a/tools/testing/selftests/bpf/prog_tests/task_fd_query_tp.c b/tools/testing/selftests/bpf/prog_tests/task_fd_query_tp.c
> index c717741bf8b6..60f92fd3c37a 100644
> --- a/tools/testing/selftests/bpf/prog_tests/task_fd_query_tp.c
> +++ b/tools/testing/selftests/bpf/prog_tests/task_fd_query_tp.c
> @@ -17,8 +17,12 @@ static void test_task_fd_query_tp_core(const char *probe_name,
>  	if (CHECK(err, "bpf_prog_test_load", "err %d errno %d\n", err, errno))
>  		goto close_prog;
>  
> -	snprintf(buf, sizeof(buf),
> -		 "/sys/kernel/debug/tracing/events/%s/id", probe_name);
> +	if (access("/sys/kernel/tracing/trace", F_OK) == 0)
> +		snprintf(buf, sizeof(buf),
> +			 "/sys/kernel/tracing/events/%s/id", probe_name);
> +	else
> +		snprintf(buf, sizeof(buf),
> +			 "/sys/kernel/debug/tracing/events/%s/id", probe_name);

Same here.

>  	efd = open(buf, O_RDONLY, 0);
>  	if (CHECK(efd < 0, "open", "err %d errno %d\n", efd, errno))
>  		goto close_prog;
> diff --git a/tools/testing/selftests/bpf/prog_tests/tp_attach_query.c b/tools/testing/selftests/bpf/prog_tests/tp_attach_query.c
> index 770fcc3bb1ba..d3e377fa8e9b 100644
> --- a/tools/testing/selftests/bpf/prog_tests/tp_attach_query.c
> +++ b/tools/testing/selftests/bpf/prog_tests/tp_attach_query.c
> @@ -16,8 +16,12 @@ void serial_test_tp_attach_query(void)
>  	for (i = 0; i < num_progs; i++)
>  		obj[i] = NULL;
>  
> -	snprintf(buf, sizeof(buf),
> -		 "/sys/kernel/debug/tracing/events/sched/sched_switch/id");
> +	if (access("/sys/kernel/tracing/trace", F_OK) == 0)
> +		snprintf(buf, sizeof(buf),
> +			 "/sys/kernel/tracing/events/sched/sched_switch/id");
> +	else
> +		snprintf(buf, sizeof(buf),
> +			 "/sys/kernel/debug/tracing/events/sched/sched_switch/id");

and here.

But perhaps the BPF folks don't care?

-- Steve

>  	efd = open(buf, O_RDONLY, 0);
>  	if (CHECK(efd < 0, "open", "err %d errno %d\n", efd, errno))
>  		return;